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‣ Diagnóstico da deficiência de fósforo em bovinos pelos exames histológicos e microrradiográficos de costelas

Pilati, Célso; Dutra, Iveraldo S.; Behrens, Konrad; Döbereiner, Jürgen; Dämmrich, Klaus
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 27-33
Português
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The objective of the present study was to show the efficiency of histologic and microradiographic techniques performed on rib bone samples as a mean of diagnosing the phosphorus status of cattle raised on phosphorus deficient pastures and receiving different mineral supplements. The rib samples were obtained from cattle of different ages which died from disease that was clinically and epidemiologically diagnosed as botulism. Ten out of 24 juvenile and adult animals studied exibited alterations of osteomalacia, while the others without those alterations served as controls. It is suggested that the method could be useful to improve the diagnosis of phosphorus deficiency of cattle in Brazil.

‣ Diagnóstico da deficiência de fósforo em ovinos pela técnica de incorporação de fósforo radioativo nos eritrócitos; Phosphorus deficiency diagnosis in sheep using labeled phosphorus uptake by erythrocytes

Antunes, Dalton Araujo; Louvandini, Helder; Silva Filho, José Cleto da; Pimentel, Concepta Margaret McManus; Dallago, Bruno Steffano; Machado, Bruno de Oliveira; Mendonça, Dharana Guedes; Corrêa, Patrícia Spoto
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Artigo de Revista Científica
Português
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Este trabalho teve como objetivo avaliar a técnica de incorporação de 32P pelos eritrócitos de ovinos jovens, mantidos em pastejo de Andropogon gayanus, como método de diagnóstico da deficiência de fósforo. Vinte ovinos, com peso vivo inicial de 13,88±2,51 kg, foram divididos em dois tratamentos de dez animais cada; num dos tratamentos, os animais foram suplementados com 3 g de P por animal por dia e, no outro, os animais não receberam suplementação de P. Foram realizadas cinco pesagens dos animais, coletas de sangue e fezes nos 8º, 29º, 43º, 57º e 71º dias do experimento, para avaliar a incorporação de 32P pelos eritrócitos, determinar as concentrações de Ca, glicose e P no soro e a porcentagem de P nas fezes. Foi encontrada diferença significativa na concentração de Ca no 57º dia. Na concentração de glicose, porcentagem de P nas fezes e peso vivo não foram observadas diferenças significativas entre os tratamentos. A partir da segunda coleta, a concentração de P no soro foi mais elevada e a incorporação de 32P foi menor no grupo de animais suplementados com P. A incorporação de 32P pelos eritrócitos é uma técnica adicional para avaliar o status de P e identificar sua deficiência subclínica em ovinos jovens. _______________________________________________________________________________ ABSTRACT; This work had the objective of evaluating the method of 32P uptake by the erythrocytes of young sheep...

‣ Multiple nitrogen and phosphorus deficiency in Zantedeschia

Fernandes,Katiúcia Dias; Paiva,Patrícia Duarte de Oliveira; Carvalho,Janice Guedes de; Resende,Aiesca Cecília; Figueiredo,Madeleine Alves de
Fonte: Editora da Universidade Federal de Lavras Publicador: Editora da Universidade Federal de Lavras
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 Português
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Multiple nutritional deficiencies are considered one of several factors that can induce doubt in the diagnosis based only in visual symptoms, because it makes identification more difficult. The aim of this work was to evaluate the development of Zantedeschia and the morphological changes resulting from nutritional disorders caused by multiple and simple nitrogen and phosphorus deficiency in plants grown in nutrient solution. Zantedeschia plants were grown for a period of eight months in a complete Hoagland and Arnon (1950) solution, with nitrogen (-N) omission, with phosphorus (-P) omission, with nitrogen and phosphorus (-NP) omission, and also nutrient solution with N and P at concentrations of 25, 50 and 75%, totalizing 7 treatments, with 4 replicates in a completely randomized experimental design. At the end of the experimental period, plant height, number of emitted leaves, leaf size, number and mineral composition of shoots were assessed. The omission of nutrients both in simple and multiple forms affected plant development. The highest shoot formation occurred in plants grown in solution and with 50% of the concentration of NP. The mineral composition of macronutrients present in leaves and shoots of plants was influenced by multiple deficiencies of N and P.

‣ Nylon Filter Arrays Reveal Differential Gene Expression in Proteoid Roots of White Lupin in Response to Phosphorus Deficiency

Uhde-Stone, Claudia; Zinn, Kelly E.; Ramirez-Yáñez, Mario; Li, Aiguo; Vance, Carroll P.; Allan, Deborah L.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /03/2003 Português
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White lupin (Lupinus albus) adapts to phosphorus deficiency (−P) by the development of short, densely clustered lateral roots called proteoid (or cluster) roots. In an effort to better understand the molecular events mediating these adaptive responses, we have isolated and sequenced 2,102 expressed sequence tags (ESTs) from cDNA libraries prepared with RNA isolated at different stages of proteoid root development. Determination of overlapping regions revealed 322 contigs (redundant copy transcripts) and 1,126 singletons (single-copy transcripts) that compile to a total of 1,448 unique genes (unigenes). Nylon filter arrays with these 2,102 ESTs from proteoid roots were performed to evaluate global aspects of gene expression in response to −P stress. ESTs differentially expressed in P-deficient proteoid roots compared with +P and −P normal roots include genes involved in carbon metabolism, secondary metabolism, P scavenging and remobilization, plant hormone metabolism, and signal transduction.

‣ Effects of Phosphorus Deficiency on the Photosynthesis and Respiration of Leaves of Sugar Beet 1

Terry, Norman; Ulrich, Albert
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1973 Português
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Phosphorus deficiency was induced in sugar beet plants (Beta vulgaris L. var. F5855441), cultured hydroponically under standardized environmental conditions, by removal of phosphorus from the nutrient supply at the ten leaf stage 28 days after germination. CO2 and water vapor exchange rates of individual attached leaves were determined at intervals after P cutoff. Leaves grown with an adequate nutrient supply attained net rates of photosynthetic CO2 fixation of 125 ng CO2 cm−2 sec−1 at saturating irradiance, 25 C, and an ambient CO2 concentration of about 250 μl l−1. After P cutoff, leaf phosphorus concentrations decreased as did net rates of photosynthetic CO2 uptake, photorespiratory evolution of CO2 into CO2-free air, and dark respiration, so that 30 days after cutoff these rates were about one-third of the control rates. The decrease in photosynthetic rates during the first 15 days after cutoff was associated with increased mesophyll resistance (rm) which increased from 2.4 to 4.9 sec cm−1, while from 15 to 30 days there was an increase in leaf (mainly stomatal) diffusion resistance (rl′) from 0.3 to 0.9 sec cm−1, as well as further increases in rm to 8.5 sec cm−1. Leaf diffusion resistance (rl′) was increased greatly by low P at low but not at high irradiance...

‣ Effect of Cycloheximide, Gamma Irradiation, and Phosphorus Deficiency on Root Pressure Exudation in Tobacco 1

Wallace, A.; Ashcroft, R. T.; Leo, M. W. M.; Wallace, G. A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1970 Português
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Cycloheximide drastically reduced the rate of root pressure exudation in detopped tobacco (Nicotiana tabacum L.), and the effect was more pronounced for nitrate salts in the external solution than for some other salts or when the roots were in water. Diurnal periodicity was greatly decreased, and its phase was changed. Effects began within an hour. Cation uptake was reduced by relatively low levels of cycloheximide. The effects of cycloheximide seemed to be reversible. Mild phosphorus deficiency resulted in decreased exudation rates from detopped tobacco and in no response to nitrate. Periodicity of exudation was not greatly affected by phosphorus deficiency, however. Gamma ray irradiation with a 60Co source at levels (up to 40-50 kiloroentgens) which are considered disruptive of moderately large molecules had relatively little effect on the exudation rate. Higher levels of irradiation, which disrupt most protein molecules, decreased exudation and obscured periodicity. The results indicate either that new protein (or peptide) synthesis is needed for the rapid nitrate transport or that the deficiency and inhibitor disrupt cellular membranes. Phosphorus deficiency increased the sensitivity of the plants to inhibition by irradiation of the exudation process.

‣ Response of Spirodela oligorrhiza to Phosphorus Deficiency

Reid, M. S.; Bieleski, R. L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1970 Português
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The duckweed Spirodela oligorrhiza, growing in sterile defined nutrient media, was used to study some responses of plants to phosphorus deficiency. On a phosphate-deficient medium, growth of Spirodela soon slowed and eventually ceased. Older leaves became chlorotic, but newly formed leaves were dark green and contained much anthocyanin. The photosynthesis rate fell gradually, roots elongated, and chloroplasts became filled with starch.

‣ Reversible changes of the muscle cell in experimental phosphorus deficiency.

Fuller, T J; Carter, N W; Barcenas, C; Knochel, J P
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1976 Português
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Both animal and human studies suggest that either phosphorus depletion or hypophosphatemia might have an adverse effect on muscle function and composition. Recently a possible deleterious effect was noted in patients with chronic alcoholism. In this unexplained disease, a variety of toxic and nutritional disturbances could affect the muscle cell, thus obscuring the precise role of phosphorus. Accordingly, we examined eight conditioned dogs for the possibility that phosphorus deficiency per se might induce an abnormally low resting transmembrane electrical potential difference (Em) and alter the composition of the muscle cell. Eight conditioned dogs were fed a synthetic phosphorus-deficient but otherwise nutritionally adequate diet plus aluminum carbonate gel for a 28-day period followed by the same diet with phosphorus supplementation for an additional 28 days. Sequential measurements of Em and muscle composition were made at 0 and 28 days during depletion and again after phosphorus repletion. Serum inorganic phosphorus concentration (mg/100 ml) fell from 4.2 +/- 0.6 on day 0 t0 1.7 +/- 0.1 on day 28. Total muscle phosphorus content (mmol/100 g fat-free dry wt [FFDW]) fell from 28.5 +/- 1.8 on day 0 to 22.4 +/- 2.1 on day 28. During phosphorus depletion...

‣ Increased Arginine Biosynthesis during Phosphorus Deficiency 1: A Response to the Increased Ammonia Content of Leaves

Rabe, Etiene; Lovatt, Carol J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1986 Português
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The accumulation of arginine in leaves of four citrus rootstock cultivars during P deficiency has been demonstrated to be due to increased de novo synthesis rather than decreased catabolism or increased protein degradation (E Rabe, CJ Lovatt, 1984, Plant Physiol 76: 747-752). In this report, we provide evidence (a) that the increased activity of the arginine biosynthetic pathway observed for citrus rootstocks grown under P-deficient conditions for 7 months is due to an increase in the concentration of ammonia in leaves of P-deficient plants and (b) that ammonia accumulation and removal through arginine systhesis are early responses to phosphorus deficiency for both a woody perennial, rough lemon (Citrus limon), and an herbaceous annual, summer squash (Cucurbita pepo). Transferring 5-day-old squash plants to a phosphorus-deficient nutrient solution for only 10 days resulted in a 2-fold increase in the concentration of nitrate in the youngest fully expanded leaves (YFE). Concomitantly, the specific activity of nitrate reductase doubled and the ammonia content of P-deficient YFE leaves increased to a concentration significantly greater that of leaves from healthy control plants (P < 0.05). Consistent with increased availability of ammonia...

‣ Diurnal Starch Accumulation and Utilization in Phosphorus-Deficient Soybean Plants 1

Qiu, Jinshu; Israel, Daniel W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1992 Português
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The effects of phosphorus deficiency on carbohydrate accumulation and utilization in 34-day-old soybean (Glycine max L. Merr.) plants were characterized over a diurnal cycle to evaluate the mechanisms by which phosphorus deficiency restricts plant growth. Phosphorus deficiency decreased the net CO2 exchange rate throughout the light period. The decrease in the CO2 exhange rate was associated with a decrease in stomatal conductance and an increase in the internal CO2 concentration. These observations indicate that phosphorus deficiency increased mesophyll resistance. Assimilate export rate from the youngest fully expanded leaves was decreased by phosphorus deficiency, whereas starch concentrations in these leaves were increased. Higher starch concentrations in phosphorus-deficient youngest fully expanded leaves resulted from a longer period of net starch accumulation and a shorter period of net starch degradation relative to those for phosphorus-sufficient controls. Phosphorus deficiency decreased sucrose-P synthase activity by 27% (averaged over the diurnal cycle), and essentially eliminated diurnal variation in sucrose-P-synthase activity. Diurnal variations in nonstructural carbohydrate concentrations in leaves and stems were also less pronounced in phosphorus-deficient plants than in controls. In phosphorus-deficient plants...

‣ Effect of Phosphorus Deficiency on Levels of Phosphorus Compounds in Spirodela

Bieleski, R. L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1968 Português
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495.622%
When Spirodela plants are transferred to a phosphate-deficient medium, growth slows down immediately, and ceases after 14 days. During this time, inorganic phosphate content falls from 30 to 0.7 μmoles/g fresh weight of tissue, phosphate ester content from 3.5 to 0.6 μmoles/g, phospholipid content from 3.5 to 1.2 μmoles/g, and residual phosphate (mainly RNA) content from 7.5 to 2.0 μmoles/g. Relative proportions of the various phosphate esters, and relative proportions of the various phospholipids, are not markedly affected by phosphate deficiency. Turnover rates of phosphate esters are somewhat higher in phosphate-deficient tissue. In control tissue, inorganic phosphate is present in 2 pools; a metabolic (12%) and a non-metabolic pool (88%). In phosphate-deficient tissues, most of the inorganic phosphate (>90%) is in the metabolic pool. Non-metabolic phosphate is presumably stored in the vacuole, and is not readily accessible to the tissue, so that growth normally occurs at the expense of external phosphate. During deficiency, growth is limited by the rate at which phosphate can be transported through the tonoplast and tissue to the growing point. Growth ceases when the supply of non-metabolic phosphate is exhausted. Metabolic phosphate is presumably located in the cytoplasm: it can not be used for growth. Nor can the plant respond to deficiency by making some phosphorus compounds at the expense of others. In this respect...

‣ Phosphorus Deficiency Decreases Cell Division and Elongation in Grass Leaves1

Kavanová, Monika; Lattanzi, Fernando Alfredo; Grimoldi, Agustín Alberto; Schnyder, Hans
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /06/2006 Português
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Leaf growth in monocotyledons results from the flux of newly born cells out of the division zone and into the adjacent elongation-only zone, where cells reach their final length. We used a kinematic method to analyze the effect of phosphorus nutrition status on cell division and elongation parameters in the epidermis of Lolium perenne. Phosphorus deficiency reduced the leaf elongation rate by 39% due to decreases in the cell production rate (−19%) and final cell length (−20%). The former was solely due to a lower average cell division rate (0.028 versus 0.046 cell cell−1 h−1) and, thus, a lengthened average cell cycle duration (25 versus 15 h). The number of division cycles of the initial cell progeny (five to six) and, as a result, the number of meristematic cells (32–64) and division zone length were independent of phosphorus status. Accordingly, low-phosphorus cells maintained meristematic activity longer. Lack of effect of phosphorus deficiency on meristematic cell length implies that a lower division rate was matched to a lower elongation rate. Phosphorus deficiency did not affect the elongation-only zone length, thus leading to longer cell elongation duration (99 versus 75 h). However, the substantially reduced postmitotic average relative elongation rate (0.045 versus 0.064 mm mm−1 h−1) resulted in shorter mature cells. In summary...

‣ Developing Rice with High Yield under Phosphorus Deficiency: Pup1 Sequence to Application1[W][OA]

Chin, Joong Hyoun; Gamuyao, Rico; Dalid, Cheryl; Bustamam, Masdiar; Prasetiyono, Joko; Moeljopawiro, Sugiono; Wissuwa, Matthias; Heuer, Sigrid
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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The major quantitative trait locus (QTL) Phosphorus uptake1 (Pup1) confers tolerance of phosphorus deficiency in soil and is currently one of the most promising QTLs for the development of tolerant rice (Oryza sativa) varieties. To facilitate targeted introgression of Pup1 into intolerant varieties, the gene models predicted in the Pup1 region in the donor variety Kasalath were used to develop gene-based molecular markers that are evenly distributed over the fine-mapped 278-kb QTL region. To validate the gene models and optimize the markers, gene expression analyses and partial allelic sequencing were conducted. The markers were tested in more than 80 diverse rice accessions revealing three main groups with different Pup1 allele constitution. Accessions with tolerant (group I) and intolerant (group III) Pup1 alleles were distinguished from genotypes with Kasalath alleles at some of the analyzed loci (partial Pup1; group II). A germplasm survey additionally confirmed earlier data showing that Pup1 is largely absent from irrigated rice varieties but conserved in varieties and breeding lines adapted to drought-prone environments. A core set of Pup1 markers has been defined, and sequence polymorphisms suitable for single-nucleotide polymorphism marker development for high-throughput genotyping were identified. Following a marker-assisted backcrossing approach...

‣ Prediction of wheat response to an application of phosphorus under field conditions using diffusive gradients in thin-films (DGT) and extraction methods

Mason, S.; McNeill, A.; McLaughlin, M.; Zhang, H.
Fonte: Kluwer Academic Publ Publicador: Kluwer Academic Publ
Tipo: Artigo de Revista Científica
Publicado em //2010 Português
Relevância na Pesquisa
471.94816%
The ability of the Diffusive Gradients in Thin Films (DGT) technique and two other established testing methods (Colwell, resin) to predict wheat responsiveness to applied P from 35 field trials across southern Australia was investigated. Regression analysis of relative early dry matter production and grain yield responses demonstrated that the DGT method predicted plant responsiveness to applied P more accurately than Colwell P and resin P at sites where maximum yields were reached with P rates used (20 out of 35). The measured concentration in soils at the DGT surface, CDGT, explained 74% of the variation in response for both early dry matter and grain, compared to 7% for early dry matter and 35% for grain using the resin P method. No significant relationships could be obtained for Colwell P although modifying the Colwell test data using Phosphorus Buffering Index resulted in a correct response prediction for 11 of the 20 field sites compared to 18 for DGT and 14 for resin P. These observations suggest that the DGT technique can assess plant available P in soils with significantly greater accuracy than traditional soil P testing methods. The critical P threshold, expressed as CDGT, was 255 μg L−1 for early dry matter and 66 μg L−1 for grain.; Sean Mason...

‣ Expanding the use of diffusive gradients in thin-films (DGT) for assessing phosphorus requirements of different crop types

Mason, S.; McNeill, A.; McLaughlin, M.
Fonte: ASA; Australia Publicador: ASA; Australia
Tipo: Conference paper
Publicado em //2010 Português
Relevância na Pesquisa
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The DGT soil test for assessing plant-available phosphorus (P) in soil has now been calibrated over three growing seasons using field-based P response trials across a range of crops (wheat, barley, canola and peas). Regression analysis of relative early dry matter production and grain yield responses demonstrated that the DGT method predicted wheat responsiveness to applied P more accurately than Colwell P and resin P. Using regression the DGT method explained 75 % of the variation in response for early dry matter and 74 % for grain. No other significant regression relationships were obtained for the other soil tests, apart from resin P which explained 40 % of the variation in response for grain. The performance of the Colwell-P test was assessed after modification using the phosphorus buffering index (PBI) and correctly predicted the crop response to P for 17 of the 30 experiments, compared to 20/30 for resin P and 26/31 for DGT. These observations suggest that the DGT technique can assess plant available P in soils with significantly greater accuracy than traditional soil P testing methods. Phosphorus response trials with other crop types including barley, canola, field peas and chickpeas have shown that different crop types have varying abilities to utilise residual P in the soil. Importantly DGT has consistently been the most accurate method for predicting P response for each of these crop types.; Sean Mason...

‣ The protein kinase Pstol1 from traditional rice confers tolerance of phosphorus deficiency

Gamuyao, R.; Chin, J.; Pariasca-Tanaka, J.; Pesaresi, P.; Catausan, S.; Dalid, C.; Slamet-Loedin, I.; Tecson-Mendoza, E.; Wissuwa, M.; Heuer, S.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
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As an essential macroelement for all living cells, phosphorus is indispensable in agricultural production systems. Natural phosphorus reserves are limited1, and it is therefore important to develop phosphorus-efficient crops. A major quantitative trait locus for phosphorus-deficiency tolerance, Pup1, was identified in the traditional aus-type rice variety Kasalath about a decade ago2, 3. However, its functional mechanism remained elusive4, 5 until the locus was sequenced, showing the presence of a Pup1-specific protein kinase gene6, which we have named phosphorus-starvation tolerance 1 (PSTOL1). This gene is absent from the rice reference genome and other phosphorus-starvation-intolerant modern varieties7, 8. Here we show that overexpression of PSTOL1 in such varieties significantly enhances grain yield in phosphorus-deficient soil. Further analyses show that PSTOL1 acts as an enhancer of early root growth, thereby enabling plants to acquire more phosphorus and other nutrients. The absence of PSTOL1 and other genes—for example, the submergence-tolerance gene SUB1A—from modern rice varieties underlines the importance of conserving and exploring traditional germplasm. Introgression of this quantitative trait locus into locally adapted rice varieties in Asia and Africa is expected to considerably enhance productivity under low phosphorus conditions.; Rico Gamuyao...

‣ Developing rice with high yield under phosphorus deficiency: Pup1 sequence to application

Chin, J.; Gamuyao, R.; Dalid, C.; Bustamam, M.; Prasetiyono, J.; Moeljopawiro, S.; Wissuwa, M.; Heuer, S.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
Relevância na Pesquisa
480.94098%
The major quantitative trait locus (QTL) Phosphorus uptake1 (Pup1) confers tolerance of phosphorus deficiency in soil and is currently one of the most promising QTLs for the development of tolerant rice (Oryza sativa) varieties. To facilitate targeted introgression of Pup1 into intolerant varieties, the gene models predicted in the Pup1 region in the donor variety Kasalath were used to develop gene-based molecular markers that are evenly distributed over the fine-mapped 278-kb QTL region. To validate the gene models and optimize the markers, gene expression analyses and partial allelic sequencing were conducted. The markers were tested in more than 80 diverse rice accessions revealing three main groups with different Pup1 allele constitution. Accessions with tolerant (group I) and intolerant (group III) Pup1 alleles were distinguished from genotypes with Kasalath alleles at some of the analyzed loci (partial Pup1; group II). A germplasm survey additionally confirmed earlier data showing that Pup1 is largely absent from irrigated rice varieties but conserved in varieties and breeding lines adapted to drought-prone environments. A core set of Pup1 markers has been defined, and sequence polymorphisms suitable for single-nucleotide polymorphism marker development for high-throughput genotyping were identified. Following a marker-assisted backcrossing approach...

‣ Andropogon grass consortium with stylo in two times: the forage response and sources of phosphorus rates

Flores, Rilner Alves; Collier, Leonardo Santos; Rodrigues dos Santos, Carlos Leandro; Montes Nogueira Borges, Bernardo Melo; Moda, Leandro Rosatto; Silva, Atila Reis da
Fonte: Univ Federal Uberlandia Publicador: Univ Federal Uberlandia
Tipo: Artigo de Revista Científica Formato: 824-832
Português
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The use of legumes intercropped with forage in the Brazilian savannah (Cerrado) region is an alternative to reverse the process of pasture degradation. The natural phosphorus deficiency in this region and the high retention capacity of this nutrient in the soil are factors that directly affect the sustainability of the production system. The objective of this study was to evaluate the effect of a phosphate with medium solubility (Arad) compared to more soluble sources such as triple superphosphate and mono-ammonium phosphate, on the formation and maintenance of pastures of Andropogon gayanus with or without the introduction of Stylosantes guianensis in pasture already established in the Brazilian savannah. Two experiments were carried out under field conditions in an Oxisol using a randomized block design with split plots, plots with two sources of phosphorus (Arad and super-triple or MAP) and subplots with different levels of phosphorus. The study showed that andropogon grass, even though characterised as forage requiring low fertilization, responded to increased fertilization, especially with the use of more soluble sources of P at planting. From the second year on, with the introduction of Stylosantes guianensis, verified effects were seen on legumes in their efficiency of utilization of residual fertilization from the first year; however...

‣ Linking physiological processes with mangrove forest structure: phosphorus deficiency limits canopy development, hydraulic conductivity and photosynthetic carbon gain in dwarf Rhizophora mangle

Lovelock, Catherine; Ball, Marilyn; Choat, Brendan; Engelbrecht, Bettina; Holbrook, Noel Michele; Feller, Ilka C
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
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Spatial gradients in mangrove tree height in barrier islands of Belize are associated with nutrient deficiency and sustained flooding in the absence of a salinity gradient. While nutrient deficiency is likely to affect many parameters, here we show that addition of phosphorus (P) to dwarf mangroves stimulated increases in diameters of xylem vessels, area of conductive xylem tissue and leaf area index (LAI) of the canopy. These changes in structure were consistent with related changes in function, as addition of P also increased hydraulic conductivity (Ks), stomatal conductance and photosynthetic assimilation rates to the same levels measured in taller trees fringing the seaward margin of the mangrove. Increased xylem vessel size and corresponding enhancements in stem hydraulic conductivity in P fertilized dwarf trees came at the cost of enhanced midday loss of hydraulic conductivity and was associated with decreased assimilation rates in the afternoon. Analysis of trait plasticity identifies hydraulic properties of trees as more plastic than those of leaf structural and physiological characteristics, implying that hydraulic properties are key in controlling growth in mangroves. Alleviation of P deficiency, which released trees from hydraulic limitations...

‣ Nitrogen metabolism in roots and leaves of green bean plants exposed to different phosphorus doses

Sánchez,E.; Ávila-Quezada,G.; Gardea,A.A.; Muñoz,E.; Ruiz,J.M.; Romero,L.
Fonte: Phyton (Buenos Aires) Publicador: Phyton (Buenos Aires)
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2009 Português
Relevância na Pesquisa
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The objective of this work was to determine the effect of different P doses on nitrogen assimilation in roots and leaves of green beans plants (Phaseolus vulgaris L. cv. Strike). Phosphorus was applied in the nutrient solution as H3PO4, at the nutrient doses of: P1 = 0.40 mM; P2 = 0.80 mM; P3 = 1.60 mM; P4 = 3.20 mM; P5 = 4.80 mM, and P6 = 6.40 mM P. Our results indicate that both P toxicity and deficiency gave similar responses to N assimilation. Phosphorus and NO3 - interacted on the absorption and translocation processes affecting N assimilation. The deficiency (P1), and toxicity (P6) treatments, diminished root absorption of NO3- in 15% and 36%, respectively, respect to the optimum dose (P3), thus reducing nutrient availability for assimilation. This result may explain the minimum enzymatic activities observed in NO3 - assimilation in P1 and P6. The minimum N assimilation observed in these treatments will eventually translate into a minimum synthesis of major N organic compound involved in plant growth and development. This will lead to a reduced plant biomass production and productivity of green beans plants.